In scanning microscopy, such as scanning transmission electron microscopy (STEM), scanning electron microscopy (SEM), or scanning probe microscopy (SPM), it is desirable to image samples consistently and with minimal image distortion. One type of distortion that occurs in scanning microscopy imaging is drift distortion. For example, thermal expansion of a sample holder, vibration, air flow, and electromagnetic fields may cause the sample to move in one or more directions while being scanned by the beam of the microscope. This movement causes distortion along one or more directions in the image. This distortion caused by sample movement during scanning is referred to as drift distortion. Drift distortion corrupts image features and can be difficult to quantify.
One possible solution to the problem of drift distortion is to correct the distortion in the final image using a-priori knowledge of the sample structure. For example, if the structure of the sample is known, distorted images can be corrected based on the known structure. However, a-priori knowledge of structural information of the sample is not always available. Accordingly, it is desirable to measure and correct drift distortion without requiring advance knowledge of sample structure.
Another method for reducing drift distortion is to wait for thermal stability of the sample holder before acquiring sample images. Such waiting reduces drift distortion caused by thermal inequilibrium of the sample and/or the sample holder with the microscope. However, waiting for thermal equilibrium before acquiring each image greatly increases the time required to obtain a series of scanned microscopy images and is undesirable for high throughput analysis.
Yet another method for reducing or correcting for drift distortion is to rapidly obtain multiple short exposure time images and average the images. While such averaging can reduce drift distortion, the final average image can still contain drift distortion, especially for large image frame sizes.
Accordingly, in light of these difficulties, there exists a need for improved methods, systems, and computer readable media for measuring and correcting drift distortion in a scanning microscopy system.